An optical element of this type is known in the form of an optical lens embodied as a spectacle lens for example from United States patent application publication 2012/0081792.
For optical lenses, in particular for spectacle lenses, plastic that is transparent in the visible spectral range is increasingly being used nowadays as material instead of silicate glass. Compared with silicate glass, plastic affords the advantages of a lower weight, a higher breaking strength, colorability and the possibility of providing rimless frames. One known disadvantage of optical lenses made of plastic, however, is that their surface area is highly susceptible to mechanical stresses and can easily be damaged by scratching.
In order to minimize this susceptibility to mechanical stresses and scratching in the case of optical lenses made of plastic, a coating including a hard lacquer layer, which is intended to protect the optical lens against mechanical effects, is applied to the plastic.
Furthermore, it is known to provide optical elements with an antireflection coating. Disturbing specular reflections can thus be avoided in the case of spectacle lenses. Antireflection coatings generally contain at least one layer made of an inorganic, oxidic material that is optically transparent. An antireflection coating can contain in particular a sequence of layers made of optically transparent, inorganic, oxidic material in which layers having a first refractive index and layers having a second refractive index, which second refractive index is higher than the first refractive index, are successively alternated.
Furthermore, it is known to embody an optical element with an antireflection coating which also protects against scratching. EP 0 698 798 A2 proposes for this purpose, for example, an antireflection coating containing a layer of borosilicate glass, which layer is vapor-deposited onto a precoated substrate body via a PVD (Physical Vapor Deposition) method.
In a coating on a substrate body made of plastic, defects can arise which are initiated by the absorption of water vapor or water molecules into the substrate body if the latter comes into contact with moisture, that is water or water vapor, but also with customary cleaning media such as alcohol or acetone.
In general, a coating has an at least passage-impeding, often even blocking effect for these substances with which in particular a spectacle lens comes into contact repeatedly over the course of its lifetime.
If these substances penetrate into an optical element for example on account of damage to the coating, that can have the consequence that, in the case of the optical element, the substrate body or else a layer applied thereto, such as a hard lacquer layer, for example, swells. Generally, in the case of the optical element, that then leads to local alterations of an optically active surface. On account of an individual scratch location, the optical element can thus easily be damaged in this way in a region extending over one square millimeter or else a number of square millimeters. In this region, an optically active surface of the optical element can also rise, often by 0.1 μm even by up to 1 μm.
It is true that the substances that penetrated into such a layer made of hard lacquer and/or a plastic body diffuse out again over time when the optical element is no longer exposed to the relevant substances. These diffusion processes lead to local volume changes, however, which in part are irreversible. They cause surface deformations, in particular, which, for example, not only bring about point and line patterns (warpage) on a coating, but also, in the case of spectacle lenses, can cause striations discernible to the naked eye under ambient lighting and furthermore also layer defects on account of mechanical stresses.